Power supply system of fuel cell vehicle

ABSTRACT

This power supply system of a fuel cell vehicle is provided with a load, a fuel cell, a power storage device, a first DC-DC converter, a second DC-DC converter, a current-measuring device, a voltage-measuring device, and a controller. The controller performs a feedback control of the first DC-DC converter such that input current or output current measured by the current-measuring device becomes a target current, and also performs a feedback control of the second DC-DC converter such that input voltage or output voltage measured by the voltage-measuring device becomes a target voltage.

BACKGROUND OF THE INVENTION

Priority is claimed on Japanese Patent Application No. 2006-146882,filed May 26, 2006, the contents of which are incorporated herein byreference.

1. Field of the Invention

The present invention relate to a power supply system of a fuel cellvehicle.

2. Description of the Related Art

A conventional power supply system of a fuel cell vehicle is known whichincreases the output voltage of a fuel cell using a first DC-DCconverter and input it to a load, wherein if the output electrical powerfrom the fuel cell is insufficient for the requirement by the load, thenthe deficiency is compensated by inputting additional electrical powerto the load from a power storage device via a second DC-DC converter,while if the output electrical power from the fuel cell is excessive forthe requirement by the load, then the excessive electrical power issupplied from the fuel cell to the power storage device via the firstDC-DC converter and the second DC-DC converter, to charge the powerstorage device (for example, refer to Japanese Unexamined PatentApplication, First Publication No. 2003-208913).

The power supply system of a fuel cell vehicle having theabove-mentioned construction needs cooperative operations of the twoDC-DC converters to supply stable current and voltage to the load; andit has been an object to establish a control method therefore.

The present invention was made in view of the above-mentionedcircumstances and has an object of providing a power supply system of afuel cell vehicle which enables a cooperative control of two DC-DCconverters to supply stable current and voltage to a load.

SUMMARY OF THE INVENTION

A power supply system of a fuel cell vehicle of the present inventionemployed the followings in order to achieve the above object.

That is, a power supply system of a fuel cell vehicle of the presentinvention includes: a load mounted on a vehicle; a fuel cell and a powerstorage device which are connected to the load so as to be parallel witheach other; a first DC-DC converter provided between the fuel cell andthe load; a second DC-DC converter provided between the power storagedevice and the load; a current-measuring device which measures one of aninput current and an output current of the first DC-DC converter; avoltage-measuring device which measures one of an input voltage and anoutput voltage of the second DC-DC converter; and a controller whichperforms a feedback control of the first DC-DC converter such that theinput current or the output current measured by the current-measuringdevice becomes a target current, and also performs a feedback control ofthe second DC-DC converter such that the input voltage or the outputvoltage measured by the voltage-measuring device becomes a targetvoltage.

According to the power supply system of a fuel cell vehicle, the firstDC-DC converter is controlled by controlling current, while the secondDC-DC converter is controlled by controlling the voltage. Since controlparameters between the first DC-DC converter and the second DC-DCconverter differ from each other, controlling of the first DC-DCconverter and controlling of the second DC-DC converter will notinterfere with each other. Accordingly, the output current of the fuelcell can be controlled so as to be stable, while enabling controllingthe input voltage to the load so as to be stable.

It may be arranged such that: the load be a motor for traveling thevehicle; and the controller increase the target voltage of the secondDC-DC converter in response to an increasing target output power of themotor.

In this case, the output power control of the motor for traveling thevehicle can be performed stably, and thereby enabling securing desiredmotor output power reliably.

The controller may be provided with: a motor target output powercalculation device which calculates the target output power of themotor; a load target voltage calculation device which calculates atarget voltage of the motor in response to the target output power ofthe motor; a fuel cell target current calculation device whichcalculates a target output current of the fuel cell; a first DC-DCconverter controller which performs a feedback control of the firstDC-DC converter referring to the target output current of the fuel cellcalculated by the fuel cell target current calculation device, as thetarget current of the first DC-DC converter; and a second DC-DCconverter controller which performs a feedback control of the secondDC-DC converter employing the target voltage of the motor calculated bythe load target voltage calculation device as the target voltage of thesecond DC-DC converter.

In this case, the voltage to the motor can be stably controlled inresponse to the motor output power, while the current of the fuel cellcan be stably controlled so as to be the desired current.

It may be arranged such that: the controller include an output powerdistribution device which distributes the target output power of themotor into an output electrical power to be generated by the fuel celland another output electrical power to be generated by the power storagedevice; and the fuel cell target current calculation device calculatethe target output current of the fuel cell based on the outputelectrical power to be generated by the fuel cell, which is distributedby the output power distribution device.

In this case, the output current of the fuel cell can be controlled inresponse to the distributed electrical power.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a general construction view of one embodiment of a powersupply system of a fuel cell vehicle of the present invention.

FIG. 2 shows a control block diagram of the same power supply system.

FIG. 3 shows one example of a PDU target voltage table utilized in theembodiment.

DETAILED DESCRIPTION OF THE INVENTION

A power supply system of a fuel cell vehicle according to one embodimentof the present invention will be explained below with reference to FIGS.1 to 3.

As shown in FIG. 1 for example, a fuel cell vehicle 10 of the presentinvention is provided with a fuel cell 11, a first DC-DC converter 12, apower storage device 13, a second DC-DC converter 14, a PDU (a PowerDrive Unit) 15, a motor (a load) 16 mounted thereon for traveling thefuel cell vehicle 10, an output power controller 17, an air-supplydevice (A/P) 18, a hydrogen tank 19 a and a hydrogen supply valve 19 b,a backpressure valve 20, a purging valve 21, a controller 22, a systemvoltage sensor (a voltage-measuring device) 31, a first voltage sensor32, a first current sensor 33, a second current sensor (acurrent-measuring device) 35, a motor rotational speed sensor 36, anaccelerator-opening degree sensor 37, and a brake pedal sensor 38.

The fuel cell 11 and the power storage device 13 are connected with themotor 16 via the PDU 15 in a parallel manner, and thereby forming apower source for the motor 16.

The motor 16 is formed, for example, by a permanent magnet typethree-phase alternating current synchronous motor that uses permanentmagnets for the magnetic field, and is controlled so as to be driven bythree-phase alternating current power supplied from the PDU 15. Whilethe fuel cell vehicle 10 is in deceleration, if driving power istransmitted from the driving wheels W to the motor 16, the motor 16 alsoworks as a generator, and produces so-called regenerative braking forceto recover the kinetic energy of the fuel cell vehicle 10 as an electricenergy.

It is well known that the motor 16 has a characteristic in which smallmotor output power can be generated by low voltage, while generatinglarge motor output power requires large voltage. On the other hand, thefuel cell 11 has a characteristic (I-V characteristic) in whichincreasing output electrical power (current) results in decreasingvoltage. Therefore, in order to obtain a large output power of the motor16 with electrical power supplied from the fuel cell 11, the outputvoltage form the fuel cell 11 needs to be increased before supplying itto the motor 16 (refer to FIG. 3). Due to this reason, the first DC-DCconverter 12 is arranged between the fuel cell 11 and the PDU 15.

In addition, the second DC-DC converter 14 is arranged between the powerstorage device 13 and the PDU 15.

The fuel cell 11 includes a plurality of layers of fuel cells, each fuelcell being an electrolytic electrode structure formed from a solidhigh-polymer electrolytic membrane formed from a cation-exchangingmembrane and the like, sandwiched between a fuel electrode (an anode)formed from an anode catalyst and a gas-diffusion layer and an oxygenelectrode (a cathode) formed from a cathode catalyst and a gas-diffusionlayer, wherein the electrolytic electrode structure is furthersandwiched between a pair separators. And these stacked fuel cells aresandwiched between a pair of end plates from both sides in the stackingdirection thereof.

Air being an oxidant gas (reaction gas) including oxygen is suppliedfrom the air-supply device (A/P) 18 to the cathode of the fuel cell 11,while fuel gas (reaction gas) including hydrogen is supplied from, forexample, the highly pressurized hydrogen tank 19 a via thehydrogen-supply valve 19 b to the anode of the fuel cell 11.

Then, hydrogen ionized by catalytic reactions on the anode catalyst ofthe anode migrates to the cathode via the suitably humidified solidhigh-polymer electrolytic membrane. In addition, electrons generatedaccompanied by this migration are extracted to an external circuit andused as direct current electrical energy. At the cathode at this time,hydrogen ions, electrons, and oxygen react and produce water.

Moreover, the hydrogen-supply valve 19 b is for example a pneumatic typeof proportional pressure control valve which takes the pressure of airsupplied from the air-supply device 18 as a signal pressure, andcontrols the pressure at the point of exit from the hydrogen-supplyvalve 19 b of the hydrogen gas passing through the hydrogen-supply valve19 b so as to be within a predetermined range that corresponds to thesignal pressure.

In addition, the air-supply device 18 having an air compressor and thelike takes air from, for example, the outside of the fuel cell vehicle10, compresses, and supplies the air as reaction gas to the cathode ofthe fuel cell 11. In addition, the rotational speed of the motor (notillustrated) which drives the air-supply device 18 is controlled by theoutput power controller 17 having, for example, a PWM inverter thatoperates in a pulse width modulation mode (PWM), based on controlinstruction sent from the controller 22. Moreover, the electrical powerto the motor of the air-supply device 18 may be supplied from any one ofthe fuel cell 11 and the power storage device 13, or may be suppliedfrom both of them.

Then, the unreacted discharged gas discharged from the hydrogendischarging outlet of the fuel cell 11 is introduced into a dilution box(not illustrated) via a discharging control valve (not illustrated)which is openably and closeably controlled by the controller 22, and isdischarged to the outside (atmosphere or the like) via the purging valve21 after the hydrogen concentration thereof is reduced in the dilutionbox to a predetermined concentration.

Moreover, a part of the unreacted discharged gas discharged from thehydrogen discharging outlet of the fuel cell 11 is introduced into acirculation path (not illustrated) having, for example, a circulationpump (not illustrated), an ejector (not illustrated), and the like.Hydrogen supplied from the hydrogen tank 19 a and the discharged gasdischarged from the fuel cell 11 are mixed, and are again supplied tothe fuel cell 11.

Then, the unreacted discharged gas discharged from an air-dischargingoutlet of the fuel cell 11 is discharged to the outside (atmosphere orthe like) via the backpressure valve 20 of which a valve opening degreeis controlled by the controller 22.

The first DC-DC converter 12 is formed so as to include, for example, achopper-type power conversion circuit which can increase the outputvoltage of the fuel cell 11. The first DC-DC converter 12 controls theoutput current IF output from the fuel cell 11, by chopping operationsfor intermitting the voltage applied to the load and the currentsupplied to the load, that is, by ON and OFF operations (switchingoperations) of a switching element provided in the chopper-type powerconversion circuit. Thus, the measurement signal output from the secondcurrent sensor 35 which measures the output current IF from the fuelcell 11 is input to the controller 22. The switching operations arecontrolled in accordance with a duty of a control pulse input from thecontroller 22 (i.e., the ratio of ON and OFF operations).

For example, the first DC-DC converter 12 increases the output voltageof the fuel cell 11 in accordance with the driving status of the fuelcell vehicle 10. In this case, the duty of the control pulse is set tothe suitable value within a range between 0% and 100%, the outputcurrent IF of the fuel cell 11 being a primary current is suitablylimited in accordance with the duty of the control pulse, and thelimited current is output as a secondary current.

Furthermore, the first DC-DC converter 12 sets a direct connectionbetween the fuel cell 11 and the PDU 15, in accordance with the drivingstate of the fuel cell vehicle 10. In this case, if the duty of thecontrol pulse is set to 100% and if the switching element is fixed toON-state, then the output voltage of the fuel cell 11 and the systemvoltage VS which is an input voltage of the PDU 15 become the equivalentvalues with each other.

The power storage device 13 is a capacitor or a battery or the likeformed from, for example, an electric double layer condenser, anelectrolytic condenser, or the like.

The second DC-DC converter 14 is formed so as to include, for example,an interactive chopper-type power conversion circuit which can increasethe terminal voltage VE and can decrease the system voltage VS of the ofthe power storage device 13. The second DC-DC converter 14 can increasethe terminal voltage VE of the power storage device 13 and can apply itto the PDU 15. Furthermore, the second DC-DC converter 14 can decreasethe system voltage VS which relates to generation of the fuel cell 11 orthe regenerating operations of the motor 16 to charge the power storagedevice 13. The second DC-DC converter 14 controls the system voltage VSbeing input voltage to the PDU 15 (in other words, applied voltage tothe motor 16), by chopping operations for intermitting the voltageapplied to the load and the current supplied to the load, that is, by ONand OFF operations (switching operations) of a switching elementprovided in the chopper-type power conversion circuit. Therefore, thedetection signals output from the system voltage sensor 31 whichmeasures the system voltage VS is input to the controller 22. Theswitching operations of the switching element are controlled inaccordance with a duty of a control pulse input from the controller 22(i.e., the ratio of ON and OFF operations).

In addition, the second DC-DC converter 14 prohibits extraction of theof the output current IE from the power storage device 13 in accordancewith the driving state of the fuel cell vehicle 10. In this case, when,for example, the duty of the control pulse input from the controller 22to the second DC-DC converter 14 is set to 0%, then the switchingelement provided in the second DC-DC converter 14 is fixed to OFF-state,and the power storage device 13 and the PDU 15 are thereby electricallydisconnected. In addition, when, for example, the duty of the controlpulse is set to a suitable value within a range between 0% and 100%, ONand OFF operations of the switching element provided in the second DC-DCconverter 14 are controlled such that the output power of the secondDC-DC converter 14 becomes zero.

The PDU 15 is provided with, for example, a PWM inverter that operatesin a pulse width modulation mode (PWM), and controls the driving and theregenerating operation of the motor 16 based on control instruction sentfrom the controller 22. This PWM inverter is provided with a bridgecircuit which is formed by connecting a plurality of, for example,transistor switching elements so as to form a bridge. While, forexample, driving the motor 16, the PWM inverter transforms the directcurrent powers output from the first DC-DC converter 12 and the secondDC-DC converter 14 to three-phase alternating current power based on thepulse width modulation signal input from the controller 22, and thensupplies it to the motor 16. On the other hand, while the motor 16 is ina regenerating operation, the three-phase alternating current poweroutput from the motor 16 is converted to the direct current power, andthe direct current power is supplied to the power storage device 13 viathe second DC-DC converter 14 to charge the power storage device 13.

The controller 22 controls the power-generating state of the fuel cell11 by outputting instructions for the pressure and the flow rate of thereaction gas supplied from the air-supply device 18 to the fuel cell 11,and an instruction for valve opening degree of the backpressure valve 20based on, for example, the driving state of the fuel cell vehicle 10,the concentration of the hydrogen contained in the reaction gas suppliedto the anode of the fuel cell 11, the concentration of the hydrogencontained in the discharged gas discharged from the anode of the fuelcell 11, and the power generating state of the fuel cell 11 (forexample, the voltage between terminals of the plurality of fuel cells,the output voltage VF of the fuel cell 11, the output current IF outputfrom the fuel cell 11, and the internal temperature of the fuel cell11).

Furthermore, the controller 22 controls an electrical power convertingoperation of the PWM inverter provided in the PDU 15. While driving themotor 16 for example, the controller 22 calculates a torque instructionwhich is an instruction value for the torque output from the motor 16,based on the measurement signal output from the accelerator-openingdegree sensor 37 which measures an accelerator opening degree AC thatcorresponds to the accelerator-driving operation amount by the driver,the measurement signal output from the brake pedal sensor 38 whichdetects whether the driver operates the brake pedal BP or not, and themeasurement signal output from the motor rotational speed sensor 36,with reference to, for example, a torque instruction map or the likewhich was set in advance so as to indicate the predeterminedrelationship of the accelerator opening degree AC, the rotational speedNM, and the torque instruction. Then, the controller 22 calculates thetarget motor output power which is necessary for making the motor 16output the torque that corresponds to the torque instruction. Then, inaccordance with the target motor output power, the controller 22 setsthe switching instruction (i.e., the pulse width modulation signal)formed from pulses for driving ON and OFF of the switching element ofthe PWM inverter, by the pulse width modulation (PWM).

When the switching instruction is input from the controller 22 to thePDU 15, the current sequentially flows through stator loop windings (notillustrated) of each phases of the motor 16. With this, the magnitude ofthe applied voltage (i.e., amplitude) and phases in U-phase, V-phase,and W-phase are controlled. Then, phase currents for U-phase, V-phase,and W-phase, which correspond to the torque instruction will be suppliedto each phases of the motor 16.

The controller 22 is input with: the measurement signal output from theaccelerator-opening degree sensor 37; the detection signal output fromthe brake pedal sensor 38; and the measurement signal output from themotor rotational speed sensor 36.

In addition, the controller 22 is provided with a power storage deviceSOC calculation device 39 which calculates the remaining capacity SOC ofthe power storage device 13 (refer to FIG. 2). The controller 22calculates the remaining capacity SOC of the power storage device 13 by,for example, calculating an integrating charging amount and anintegrating discharging amount by integrating the charging current andthe discharging current of the power storage device 13 for eachpredetermined time interval, and by adding these integrating chargingamount and integrating discharging amount to a remaining capacity at theinitial state or the before of starting charging and discharging, orsubtracting these integrating charging amount and integratingdischarging amount from the remaining capacity at the initial state orthe before of starting charging and discharging.

The controller 22 is input with measurement signals output from thefirst voltage sensor 32 which measures the terminal voltage VE of thepower storage device 13, and the first current sensor 33 which measuresthe charging current and the discharging current of the power storagedevice 13.

Then, the controller 22 outputs a control pulse for controlling theelectrical power converting operations of the first DC-DC converter 12in accordance with the target motor output power and the remainingcapacity SOC of the power storage device 13, controls the output currentIF output from the fuel cell 11, outputs the control pulse forcontrolling the electrical power converting operations of the secondDC-DC converter 14, and thereby controls charging and discharging of thepower storage device 13.

In this fuel cell vehicle 10, if a predetermined condition is satisfiedwhile driving the motor 16, then power-assisting (assist) is executed bythe power storage device 13 to supply electrical power from both of thefuel cell 11 and the power storage device 13 to the motor 16. At thistime, it is necessary to increase the output electrical power of thefuel cell 11 by the first DC-DC converter 12, and to increase the outputelectrical power of the power storage device 13 by the second DC-DCconverter 14. Accordingly, the controller 22 needs to control the firstDC-DC converter 12 and the second DC-DC converter 14 at the same time.

In this case, one may employ a control method including: a feedbackcontrol in which an output electrical power of the first DC-DC converter12 is measured, and the measured output voltage is controlled so as tobe the target input voltage to the PDU 15; and another feedback controlin which an output electrical power of the second DC-DC converter 14 ismeasured, and the measured output voltage is controlled so as to be thetarget input voltage to the PDU 15. However, such control method willcause unstable voltages due to interference between the voltage controlsof the first DC-DC converter 12 and the second DC-DC converter 14, andthereby causing difficulties in controlling the output voltage of thefuel cell 11 and in controlling the input voltage to the PDU 15.

Therefore, in the power supply system of a fuel cell vehicle of thepresent embodiment, the first DC-DC converter 12 performs a feedbackcontrol based on current, while the second DC-DC converter 14 performsanother feedback control based on voltage, and thereby preventing theinterference of the controls therebetween.

The detailed explanation will be made hereinbelow with reference to ablock diagram shown in FIG. 2.

Firstly, the motor target output power calculation device 41 calculatesthe torque instruction which is an instruction value for the torqueoutput from the motor 16, based on: the measurement signal output fromthe accelerator-opening degree sensor 37, which corresponds to theaccelerator-opening degree; the detection signal output from the brakepedal sensor 38; and the measurement signal that corresponds to themotor rotational speed and is output from motor rotational speed sensor36, with reference to the torque instruction map or the like which wasset in advance so as to indicate the predetermined relationship of theaccelerator opening degree AC, the rotational speed NM, and the torqueinstruction. As a result, the motor target output power calculationdevice 41 calculates the motor target output power which is necessaryfor the motor 16 to output the torque corresponding to the torqueinstruction.

Controls of the second DC-DC converter 14 will be explained below.

The PDU target voltage calculation device (a load target voltagecalculation device) 42 calculates the target voltage to the PDU 15 thatcorresponds to the motor target output power calculated by the motortarget output power calculation device 41 (that is, the target voltageto the motor 16), with reference to the PDU target voltage table shownin FIG. 3. In the PDU target voltage table shown in FIG. 3, the targetvoltage to the PDU 15 is set so as to increase in response to theincreasing motor target output power, in accordance with the outputcharacteristics of the motor 16.

The controller 22 performs a feedback control of the second DC-DCconverter 14 such that the system voltage VS measured by the systemvoltage sensor 31 agrees with the target voltage of the PDU 15calculated by the PDU target voltage calculation device 42.

Next, controls of the first DC-DC converter 12 will be explained below.

The output power distribution device 43 determines the most suitablepower distribution between the output electrical power by the fuel cell11 and the output electrical power by the power storage device 13, forsupporting the motor target output power calculated by the motor targetoutput power calculation device 41, considering the remaining amount SOCof the power storage device 13 calculated by the power storage deviceSOC calculation device 39. That is, the output power distribution device43 determines the distribution of the output electrical power of thefuel cell 11 and the output electrical power of the power storage device13.

In addition, the fuel cell target current calculation device 44calculates the target current output from the fuel cell 11 (in otherwords, the target current input to the first DC-DC converter 12) basedon the output power of the fuel cell 11 determined by the output powerdistribution device 43, considering the current limitation value whichis an input signal from a fuel cell controller (not illustrated) and isextractable from the fuel cell 11.

Then, the controller 22 performs a feedback control of the first DC-DCconverter 12 such that the output current IF of the fuel cell 11measured by the second current sensor 35 meets the target currentcalculated by the fuel cell target current calculation device 44.

As has been explained in the above, the first DC-DC converter 12connected to the fuel cell 11 performs the feedback control of thecurrent so as to be the target current, while the second DC-DC converter14 connected to the power storage device 13 performs another feedbackcontrol of the voltage so as to be the target voltage; therefore, sincethe first DC-DC converter 12 and the second DC-DC converter 14 controldifferent parameters with each other, the controls therebetween will notinterfere with each other.

Accordingly, the output current of the fuel cell 11 can be controlledstably and the input voltage to the PDU 15 can be controlled stably.

In addition, since the target voltage to the PDU 15 set in the PDUtarget voltage calculation device 42 is increased in accordance withincreasing motor target output power, the desired motor output can besecured reliably.

As a result, it is possible to perform the output control of the motor16 being the driving motor of the fuel cell vehicle 10.

Moreover, the present invention is not limited only to theabove-mentioned embodiment.

For example, in the above-mentioned embodiment, the control parameterthat should be controlled by the first DC-DC converter 12 is set to bethe output current of the fuel cell 11 (in other words, the inputcurrent of the first DC-DC converter 12); however, the output current ofthe first DC-DC converter 12 may be the control parameter thereinstead.In addition, in the above-mentioned embodiment, the control parameterthat should be controlled by the second DC-DC converter 14 is set to bethe output voltage of the second DC-DC converter 14; however, the inputvoltage of the second DC-DC converter 14 may be the control parameterthereinstead.

While a preferred embodiment of the invention has been described andillustrated above, it should be understood that this is an exemplary ofthe invention and is not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

1. A power supply system of a fuel cell vehicle comprising: a loadmounted on a vehicle; a fuel cell and a power storage device which areconnected to the load so as to be parallel with each other; a firstDC-DC converter provided between the fuel cell and the load; a secondDC-DC converter provided between the power storage device and the load;a current-measuring device which measures one of an input current and anoutput current of the first DC-DC converter; a voltage-measuring devicewhich measures one of an input voltage and an output voltage of thesecond DC-DC converter; and a controller which performs a feedbackcontrol of the first DC-DC converter such that the input current or theoutput current measured by the current-measuring device becomes a targetcurrent, and also performs a feedback control of the second DC-DCconverter such that the input voltage or the output voltage measured bythe voltage-measuring device becomes a target voltage.
 2. The powersupply system of a fuel cell vehicle according to claim 1, wherein: theload is a motor for traveling the vehicle; and the controller increasesthe target voltage of the second DC-DC converter in response to anincreasing target output power of the motor.
 3. The power supply systemof a fuel cell vehicle according to claim 2, wherein the controllercomprises: a motor target output power calculation device whichcalculates the target output power of the motor; a load target voltagecalculation device which calculates a target voltage of the motor inresponse to the target output power of the motor; a fuel cell targetcurrent calculation device which calculates a target output current ofthe fuel cell; a first DC-DC converter controller which performs afeedback control of the first DC-DC converter referring to the targetoutput current of the fuel cell calculated by the fuel cell targetcurrent calculation device, as the target current of the first DC-DCconverter; and a second DC-DC converter controller which performs afeedback control of the second DC-DC converter employing the targetvoltage of the motor calculated by the load target voltage calculationdevice as the target voltage of the second DC-DC converter.
 4. The powersupply system of a fuel cell vehicle according to claim 3, wherein: thecontroller comprises an output power distribution device whichdistributes the target output power of the motor into an outputelectrical power to be generated by the fuel cell and another outputelectrical power to be generated by the power storage device; and thefuel cell target current calculation device calculates the target outputcurrent of the fuel cell based on the output electrical power to begenerated by the fuel cell, which is distributed by the output powerdistribution device.